(1) Field of the Invention
The present invention relates to charge coupled device (CCD) solid-state imaging devices and driving methods of the CCD solid-state imaging devices and, in particular, to a technique of transferring charges in a column direction.
(2) Description of the Related Art
Recent solid-state imaging devices have achieved high pixel density of 10 million pixels or more, which allows a user to capture a moving image, and a still image as clear as a photo based on silver photography. As the pixel density becomes higher, a pitch of a unit pixel size of a solid-state imaging device becomes smaller than 2 μm, which makes the unit pixel size even finer. Described hereinafter are a structure of a conventional solid-state imaging device and a driving method of the solid-state imaging device (See Patent Reference 1: Japanese Unexamined Patent Application Publication No. 62-076764, for example) with reference to a charge-transfer (CCD) solid-state imaging device.
FIG. 24 shows a schematic block diagram of a conventional CCD solid-state imaging device.
The solid-state imaging device includes photo diodes 902 arranged two-dimensionally (in a matrix), column CCDs 903 for transferring signal charges (pixel signals) read out from the photo diodes 902, an address circuit 904 which selects, per row, the photo diodes 902 for the reading out, and drains 915 formed separately from the column CCDs 903. Transfer of the charges to the drains 915 is controlled by a transfer pulse applied to transfer electrodes 905 and 906, and control gates (drain gate) 914. The transfer electrodes 905, 906, and the control gate 914 are respectively formed in rows (lines), and connected to terminals 918, 919, and 916 with a separate line.
In such a solid-state imaging device, the signal charges, transferred by the column CCDs 903, are transferred from an end of the column CCDs 903 to a row CCD 911 by the transfer electrodes 905 and 906. Concurrently, smear charges are swept from the column CCDs 903 to the drains 915 by the transfer electrodes 905 and the control gates 914. The transfer electrodes 905, 906, and the control gates 914 are connected with a separate line. Thus, for an image, the above sequence of operations is typically controlled per row.